1. The Field of the Invention
The present invention generally relates to rotating machinery. In particular, some example embodiments relate to an x-ray tube bearing assembly including magnetic bearing assembly components and ball bearing assembly components.
2. The Related Technology
The x-ray tube has become essential in medical diagnostic imaging, medical therapy, and various medical testing and material analysis industries. Such equipment is commonly employed in areas such as medical diagnostic examination, therapeutic radiology, semiconductor fabrication, and materials analysis.
An x-ray tube typically includes a vacuum enclosure that contains a cathode assembly and an anode assembly. The vacuum enclosure may be composed of metal such as copper, glass, ceramic, or a combination thereof, and is typically disposed within an outer housing. At least a portion of the outer housing may be covered with a shielding layer (composed of, for example, lead or a similar x-ray attenuating material) for preventing the escape of x-rays produced within the vacuum enclosure. In addition a cooling medium, such as a dielectric oil or similar coolant, can be disposed in the volume existing between the outer housing and the vacuum enclosure in order to dissipate heat from the surface of the vacuum enclosure. Depending on the configuration, heat can be removed from the coolant by circulating the coolant to an external heat exchanger via a pump and fluid conduits. The cathode assembly generally consists of a metallic cathode head assembly and a source of electrons highly energized for generating x-rays. The anode assembly, which is generally manufactured from a refractory metal such as tungsten, includes a target surface that is oriented to receive electrons emitted by the cathode assembly.
During operation of the x-ray tube, the cathode is charged with a heating current that causes electrons to “boil” off the electron source or emitter by the process of thermionic emission. An electric potential on the order of about 4 kV to over about 116 kV is applied between the cathode and the anode in order to accelerate electrons boiled off the emitter toward the target surface of the anode. X-rays are generated when the highly accelerated electrons strike the target surface.
In a rotating anode-type x-ray tube, the anode is supported by a bearing assembly that allows the anode to rotate within the x-ray tube. One type of bearing assembly sometimes used in x-ray tubes is a ball bearing assembly. While conventional ball bearing assemblies can be relatively inexpensive, they can also be relatively noisy and the noise can be a source of discomfort or irritation for medical patients and other x-ray tube users and operators. Another type of bearing assembly sometimes used in x-ray tubes is a magnetic bearing assembly. While conventional magnetic bearing assemblies can be relatively quiet, they can also be relatively expensive, increasing the cost of x-ray tubes in which they are used.
Further, a substantial amount of heat can be generated in rotating anode-type x-ray tubes from the high electrical power used to operate the x-ray tubes. For example, rotating anodes in some x-ray tubes may regularly experience temperatures exceeding 1200° C. due, at least in part, to the impingement of the highly accelerated electrons on the rotating anode. The high temperatures can cause shifting of portions of the anode, cracking, distressing, warping, and other material failures. Material failures can result in errors in the resultant x-ray image. Consequently, heat must be managed in many x-ray tubes
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced